Life with humans changed dogs in some dramatic ways, and it didn’t take long.

Our best friends come in a fantastic array of shapes and sizes; a Borzoi looks nothing like a Boston terrier, except for a certain fundamental, ineffable (except to taxonomists) doggyness about them. And it’s been that way almost from the beginning. A recent study of dog and wolf skulls from the last 50,000 years found that dogs living just after the last Ice Age were already about half as varied in their shape and size as modern dogs.

“Shaped like a friend” means a lot of different things

Biologist and archaeologist Allowen Evin, of CNRS, and her colleagues compared the size and shape of 643 skulls from dogs and wolves: 158 from modern dogs, 86 from modern wolves, and 391 from archaeological sites around the world spanning the last 50,000 years. By comparing the locations and sizes of certain skeletal landmarks, such as bony protrusions where muscles attached, the researchers could quantify how different one skull was from another. That suggested a few things about how dogs, or at least the shapes of their heads, have evolved over time.

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